Field of the Invention
The invention pertains to the field of high-precision measuring devices. More particularly, the invention pertains to a high-precision system for loading and for rotational and axial movement of a sample.
Description of Related Art
There are many fields where precise sample control, positioning, and manipulation is critical, including, but not limited to, tomography, microscopy, materials testing, and micro-machining.
Tomography is a non-destructive, non-invasive method of imaging a three-dimensional object. A tomograph images a sample by sectioning through the sample using a penetrating wave. X-rays or gamma rays are commonly used as the penetrating wave, but radio-frequency waves, electron-positron annihilation, electrons, ions, magnetic particles, or neutrons may also be used. A mathematical process called tomographic reconstruction is used to generate an image from the data produced by sectioning the sample by the penetrating wave. X-ray computed tomography, computed tomography (CT scan), or computed axial tomography (CAT scan) are commonly used medical imaging procedures.
In the case of x-ray tomography, the imaging of a sample depends on the absorption of x-rays by the sample. The sample is placed between the x-ray source and an x-ray detector, which measures the attenuation in the transmitted rays. Either the detector or the sample may be fixed in location. With conventional fixed detector systems, the stage on which the sample is mounted is rotated up to 180 or 360 degrees. Radiographs of the sample are collected on the detector at different time points as the stage rotates. The image obtained at each angle includes a matrix of pixels. The intensity of each pixel is a function of the linear absorption coefficient, which in turn depends on the chemical and physical makeup of the sample. Back-propagation and other advanced de-convolution methods may be used to provide a three-dimensional intensity file to reconstruct an image representing the sample from the radiographs, which is conventionally done one slice at a time. A complete three-dimensional image is conventionally obtained by stacking axial slices together.
The resolution of a tomograph is dependent on the fineness of the control of the positioning and movement of the sample stage and the beam source. The best conventional high-precision tomographs only have a measurement resolution to the micron level.
In materials testing, it is advantageous to perform tests on a sample that is under a controlled load, such as a tensile load or a compressive load. It is important to be able to apply a controlled, known load to a sample being tested.